Origin story: Duke of York Restaurant, by Nex

Alan Dempsey of Nex on a design that unfurled from a grade II-listed wall 

We were always conscious of how to intervene in this kind of public space in a way that is sensitive to its context but also unapologetically contemporary. The site for the restaurant is a square next to the former Duke of York’s barracks in Chelsea, opposite the King’s Road, and it’s all grade II-listed.

We really didn’t want to lose that public space – if anything we wanted to enhance it. The neighbouring parade ground has this amazing ribbon of trees all the way round it, but it was interrupted by our site, so we thought maybe there was a way to green that gap, and give people another perspective over the whole space. That resulted in thinking about the roof as a public space, directly connected to, but slightly removed from, the square and parade ground. 

Our other starting point was a grade II-listed wall, which was originally part of the military asylum but since the barracks’ redevelopment had become a bit of an odd appendage to the square. We needed to address this wall but we didn’t want the building to have a distinctive front or back – it needed to be approachable from any direction.

We came up with the notion of continuing the wall, but curling it into a ribbon: a layered space from outside to inside, from the square to a central service core, with large openings on all sides. As we looked into the idea of the wall, materiality became increasingly important. We considered brick, structural steel, or a steel frame with cladding. But it really needed an integrity to it, to be both structure and finish. We felt a precast concrete solution gave us these benefits. It has a sense of solidity but at the same time it can span 10-12m openings, and it meant we could minimise the work done on site.

But we also wanted it to convey the sense of a ribbon – so it needed to be as slender as possible. In engineering codes, you quickly come up against a 200mm minimum thickness for structural concrete columns and walls, but we worked very closely with AKT II to get that down to 150mm. As a public roof space, it’s carrying significant loads, but it does it effortlessly, which belies the sheer quantity of reinforcement in the columns and how hard the connections are working.

We chose a white concrete, with an off-white fine aggregate of quartz and a coarse aggregate of dolomite. The front and back surfaces have been acid-etched to give a slight lustre to the quartz – with curved concrete, you really want to do as little finishing as possible. But within the arches, we heavily ground and polished the reveals to show the pale-grey and blue dolomite stones.

Conceptually, it reinforces the idea of a continuous ribbon being cut to form these openings. The structural glazing is a unique system: these big, curved panels, 3.2m high and 9.5m wide, lower into the basement on a counterweight, just like a sash window. They depend on extremely low tolerances in the concrete frame, which was another reason why we chose precast. We had to coordinate very closely between the glass manufacturer in Switzerland and the concrete manufacturer in Derby to be certain that the elements would all fit together precisely on site.

The windows give a sense of performance – the restaurant (called Vardo) is a great place to watch the world go by, and to be seen as well. The way we’ve had to abandon these gathering places in the last few months is a real reminder of how they are the essence of the culture of cities. With its open facade and roof, Vardo was meant to come into its own in spring and summer. We’ll have to save that for another year, but hopefully it will be lively and animated very soon.

Alan Dempsey is founding director of London-based architect Nex. Interview by Nick Jones

Photos James Brittain